Anita Hill, photographed at Brandeis University, is the subject of a documentary, “Anita.” (CreditTony Cenicola/The New York Times)

WALTHAM, Mass. — On the day in 1991 that the Senate confirmed Clarence Thomas to the Supreme Court, Anita Hill — the little-known law professor who riveted the nation by accusing him of sexual harassment — faced news cameras outside her simple brick home in Norman, Okla., with her mother by her side, and politely declined to comment on the vote. In the nearly 23 years since, Ms. Hill, now a professor of social policy, law and women’s studies at Brandeis University, has worked hard, she likes to say, to help women “find their voices.” She has also found hers — and she is not afraid to use it.

“I believe in my heart that he shouldn’t have been confirmed,” she said in a recent interview, acknowledging that it irritates her to see Justice Thomas on the court. “I believe that the information I provided was clear, it was verifiable, it was confirmed by contemporaneous witnesses that I had talked with. And I think what people don’t understand is that it does go to his ability to be a fair and impartial judge.”

It was a surprisingly candid comment from a deeply private woman who has long been careful in the spotlight. But the quiet life Ms. Hill has carved out for herself is about to be upended — by her own choice — with the release of a documentary, Anita, opening on March 21 in theaters in Los Angeles, San Francisco and New York.

For those too young to remember, Ms. Hill was the reluctant witness in the explosive Thomas hearings, the young African-American lawyer in the aqua suit, grilled in excruciatingly graphic detail by an all-white, all-male Senate Judiciary Committee. The hearings transformed the country, sparking a searing conversation about sexual harassment, as well as Ms. Hill, who was vilified as a liar by conservatives but ultimately embraced, as the film shows, by a new generation of young women.

Directed by the Academy Award winner Freida Mock, the documentary — which does not reveal Ms. Hill’s current views on Justice Thomas — chronicles her plunge, and the nation’s, into a volatile stew of sex, race and politics. For the professor, the film is a chance to show the public (and on a deeply personal level, her large extended family) that she has survived, thrived and, as she says, “moved on.”

Yet like Anita the person, Anita the movie is bound to unleash raw feelings in Washington. Some conservative Republicans still revile Ms. Hill. Some Democrats — including Vice President Joseph R. Biden Jr., who “did a terrible job” running the hearings, in Ms. Hill’s view — would probably like to forget her.

A spokeswoman for Mr. Biden said the vice president “continues to wish nothing but the best for Anita Hill.” Justice Thomas, who supervised Ms. Hill at two federal agencies and has categorically denied her accusations, declined to comment. (In his 2007 autobiography, he referred to Ms. Hill as “my most traitorous adversary.”) But his backers, who include some devoted female former clerks, are not shy about speaking out.

“I honestly think she’s just making it up,” said Carrie Severino, a former Thomas clerk and chief counsel of the Judicial Crisis Network, an advocacy group. “I think she’s built her career on that story. She is using that and using him as a way of boosting her own career, and that’s really shameful.”

One subject Ms. Hill will not address is Justice Thomas’s voting record. If a backlash is coming, she said, she is ready. During an hourlong conversation in an airy gallery in Brandeis’s Rose Art Museum, she listened to Ms. Severino’s critique, thought for a moment, then smiled wryly. “I’ve heard worse,” she finally said.

At 57, Ms. Hill, the youngest of 13 children from a rural Oklahoma farm family, is in many ways the same poised, dignified woman America met 23 years ago. She has the same lyrical voice, the same way of answering questions with perfect precision and gentle pushback. (Asked if she voted for Vice President Biden, whom she faults for failing to call other women and harassment experts as witnesses, she laughed and said, “I voted for President Obama.”)

Yet she is also profoundly changed.

“I think this event changed the course of her life and gave her a public mission that she took on,” said Fred Lawrence, the Brandeis president and a Yale Law School classmate of Ms. Hill’s. “It’s not a duty that she volunteered for, but I think she understood that the circumstances had put her in a unique role, and gave her a voice.”

The hearings were a surreal spectacle, as senators prodded an obviously uncomfortable Ms. Hill through awkward testimony about penis size, pubic hair and a pornographic film star known as Long Dong Silver — shocking public discourse at the time. When the hearings ended, Ms. Hill returned to teaching commercial law at the University of Oklahoma, trying, as she says in the film, to find “a new normal.” It proved difficult.

Ms. Hill at the hearings. (CreditAmerican Film Foundation)

There were thousands of letters of support, but also death threats, threats to her job. Conservative state lawmakers wanted her fired; fortunately, she had tenure. Even years later, she felt “a discomfort,” she said. One dean confided that he had tired of hearing colleagues at other schools remark, “Isn’t that where Anita Hill is?”

In Washington, her testimony reverberated. Sexual harassment claims shot up. “Our phones were ringing off the hook with people willing to come forward who had been suffering in silence,” said Marcia D. Greenberger, founder and co-president of the National Women’s Law Center in Washington, where Ms. Hill serves on its board.

Congress passed a law allowing victims of sex discrimination to sue for damages, just as victims of racial discrimination could. Waves of women began seeking public office. In 1991, there were two female senators. Today there are 20.

But if Washington moved on, Ms. Hill could not. Once, in an Oklahoma airport, she bumped into Arlen Specter, the Pennsylvania senator who had accused her of perjury and who died in 2012. He said maybe they could work together on some things, that she should call him. Ms. Hill was astonished; she never did. Just one senator, Paul Simon of Illinois, made amends; before he died, he sent Ms. Hill his autobiography with a nice inscription.

“For them, it’s all about politics,” she said. “For me, it was about my life.”

She published a memoir in 1997; the following year, she joined Brandeis, teaching courses and pursuing research on gender and racial inequality. Years passed; her notoriety receded. Today, many of her students have no idea who Anita Hill is.

“I had to Google it,” said one, Megan Madison, who considers Ms. Hiants young people to know. She had previously resisted entreaties from filmmakers, she said. But in 2010, with the 20th anniversary of the hearings approaching, she decided it was time “to revisit this, and for people to understand wh.”

A friend introduced her to Ms. Mock, whose 1994 film about the architect Maya Lin won an Oscar for best feature documentary. With Ms. Hill, the director said, she wanted to tell “the story of an ordinary person who does an extraordinary act.”

The movie, which premiered at Sundance last year to good reviews, opens with the voice of Justice Thomas’s wife, Ginni, in a 2010 message on Ms. Hill’s office answering machine, asking her to “consider an apology and some full explanation of why you did what you did with my husband.” (Ms. Hill initially thought it was a prank.) It intersperses old footage of the hearings with interviews with Ms. Hill; her lawyer, the Harvard law professor Charles J. Ogletree Jr.; some supporters and two journalists, Jill Abramson, now executive editor of The New York Times, and Jane Mayer of The New Yorker, co-authors of a 1994 book, “Strange Justice,” that raised questions about Justice Thomas’s candor.

The film follows Ms. Hill through a 20th-anniversary commemoration, where awe-struck young women, some in tears, thank her and praise her courage. Emily May, a co-founder of Hollaback!, a nonprofit group that fights street harassment, was among them.

“We all felt like we were seeing this legend,” Ms. May said.

The movie also offers a glimpse, albeit a thin one, into Ms. Hill’s private life. Viewers learn that she has kept the aqua linen suit (the Smithsonian has asked for it, but she is “still very protective,” she said); watch her attend a joyful family wedding; and discover that she has a longtime companion, the businessman Chuck Malone, about whom she will say little.

She wears a diamond band, a gift from him, on her left ring finger. “I know,” she said, laughing. “Everybody sees this ring. I guess I’m not such a traditionalist as to think that I need to, at this moment, marry.”

Today, Ms. Hill is working mostly on a strategic plan for Brandeis; she plans to use a sabbatical next year to organize her letters. If she has a legacy, experts say, it is in creating a vocabulary for Americans to talk about sexual harassment, where none existed before. In 1991, after a confidential memo containing Ms. Hill’s accusations leaked out, seven female Democratic House members marched over to the Senate to demand that she be called as a witness.

“I can’t even imagine a hearing today where a woman would come forth with an accusation of sexual harassment, and it would be ignored,” said Representative Nita Lowey, the New York Democrat who was among them. “Today, we probably would have thousands of women from all over the country march to the Capitol.”

As women in the military and on college campuses grapple with sexual assault, Ms. Lowey said there was still more work to be done. Ms. Hill agrees.

But she wants America to know that “I have a good life,” a life of meaning and purpose, that “something positive” has come out of those dark 1991 days. Looking back, she said, she sometimes marvels at how hard her critics worked to destroy her.